This invention relates to a dry-etching apparatus which can etch aluminum wiring films on wafers of integrated circuit elements, and can provide a post-treatment in which etching resist films are removed together with the chlorides deposited on the surface of the wafers during the etching process.
A dry-etching apparatus with a parallel, flat electrode system provided with vacuum antechambers before and after an etching chamber has been proposed as a dry-etching apparatus for the etching of the aluminum wiring films formed of wafers of integrated circuit elements.
One side of this dry-etching apparatus is provided with a first vacuum antechamber in which a wafer-feed unit holding therein a cassette containing a plurality of wafers, and the other side thereof is provided with a second vacuum antechamber in which a recovery unit holding therein a cassette containing a plurality of etched wafer. Shutters are provided at the entrances and exit of the vacuum antechambers, and between the vacuum antechambers and an etching chamber. Each of the vacuum antechambers is provided with an internal transfer means by which the wafers are transferred from the feed unit to the etching chamber, and then to the recovery unit therefrom.
In such a dry-etching apparatus, a cassette containing wafers is held in the feed unit, and an empty cassette in the recovery unit, and the vacuum antechambers are then evacuated in such a manner that the pressure in the vacuum antechambers is lower than that in the etching chamber. The shutter between the first vacuum antechamber and the etching chamber is then opened so that a wafer can be removed from the cassette in the wafer feed unit, and the wafer is supplied to the etching chamber. The shutter is then closed and the etching of the wafer performed. When the etching is completed, the shutter between the etching chamber and the second vacuum antechamber is opened so that the etched wafer can be removed from the etching chamber and stored in the cassette in the recovery unit. When the etching of a required number of wafers is completed, and the etched wafers have been stored in the cassette, the shutter at the exit of the second vacuum antechamber is opened, and the cassette is removed therefrom and sent on to a post-treatment stage. In the post-treatment stage, chlorides deposited on the surface of the wafers and the etching resist films are removed in a plasma atmosphere using oxygen as a reaction gas.
This dry-etching apparatus, in which the etched wafers is removed into the atmosphere, has the following problems.
In the regular dry etching of aluminum, a chloride gas, such as carbon tetrachloride or boron tetrachloride, is used as the etching reaction gas. When etching is done with such a gas, chlorides are deposited on the wafers and the resist films formed thereon. These chlorides have an extremely high hydroscopicity. Accordingly, when the chlorides come into contact with the atmosphere, they absorb the water contained therein and dissolve, so that chlorine ions are generated. The chlorine ions react with the aluminum to dissolve it, which results in breaks in the wiring of the integrated circuit elements.